<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
		/* 2n为偶数列   2n+1为奇数列   -n+5为前五个 n+5为第五个以后*/
			li:nth-child(n+5){
					background-color: #008000;
				
				
			}
		</style>
		 
		
		
	</head>
	<body>
		<ul>
			<li>1</li>
			<li>2</li>
			<li>3</li>
			<li>4</li>
			<li>5</li>
			<li>6</li>
		</ul>
	</body>
</html>
